Victorian House - Trench to reduce ground level

[dannyg]

Good morning all,

The ground level on one side of my house is too high and nearly compromising the original DPC. I have spent last couple of days breaking up concrete path and making sure ground levels are at least 150mm below DPC. I have been following this very informative post here

Image here

As you can see from image, the brown paint indicates where ground level was before I dug down. My question now is what I do going forward. Drainage is pretty good. There has been torrential rain for last few days and only a couple of small pools of water have formed in the trench and disappeared 30 minutes when it's stopped raining. My though process is this;
- compact soil in trench and add crushed stone
- line with landscape fabric to suppress weeds
- fill with gravel/stones to help with drainage

Would you recommend that I add corrugated pipe and cap into existing drain? I want to avoid this if not necessary as they are old clay pipes which are brittle.

Also am I on the right track here and is there anything you disagree with my approach?

Cheers all

 

[noj]

All good so far, but filling the trench back in above the dpc and/or compacting the base potentially recreates the problem.

Seems like a place for the famed (around these parts) Zebcolm Trench.

The Zebcolm Trench

The Zebcolm trench is so named because I made one, and then malcolm made one. If you make one, let us know and we can elongate the name. The Problem: ground levels higher on the outside than inside, causing penetrating damp through solid wall, with no possibility of lowering external ground...

www.periodproperty.co.uk

 

[dannyg]

Many thanks for your reply. Yes my plan was only fill with stone up to around 50mm below air vent half way along wall. Similar to this.

 

[Lacan07]

Good morning all,

The ground level on one side of my house is too high and nearly compromising the original DPC. I have spent last couple of days breaking up concrete path and making sure ground levels are at least 150mm below DPC. I have been following this very informative post here

Image here

As you can see from image, the brown paint indicates where ground level was before I dug down. My question now is what I do going forward. Drainage is pretty good. There has been torrential rain for last few days and only a couple of small pools of water have formed in the trench and disappeared 30 minutes when it's stopped raining. My though process is this;
- compact soil in trench and add crushed stone
- line with landscape fabric to suppress weeds
- fill with gravel/stones to help with drainage

Would you recommend that I add corrugated pipe and cap into existing drain? I want to avoid this if not necessary as they are old clay pipes which are brittle.

Also am I on the right track here and is there anything you disagree with my approach?

Cheers all

I wouldn't add soil. To save some money you can crush up some old bricks, fill most of the way, and then top with a decorative stone / pebble of your choice.

 

[Zebra]

Leave it open if you can. Anything solid, no matter how free draining, such as gravel, stones, etc will retain moisture against the wall of the house. I would consider building a tiny retaining wall or curb-type edge to create a change in levels, as per the Zebcolm trench, even though yours is much shallower.
If it's only the water that actually falls into it that you're dealing with, then that is negligible and you don't need to add any sort of corrugated pipe. Such measures would only be necessary if the ground was falling towards the trench and thus filling it with water from elsewhere, and even then the corrugated pipe might be better located further from the house. But unless you're dealing with a lot of water then it would most likely do nothing.

 

[Zebra]

Many thanks for your reply. Yes my plan was only fill with stone up to around 50mm below air vent half way along wall. Similar to this.

Yes, that looks good, though timber is obviously not the ideal choice of material for the long-term in that location... but if you accepted that then the concept looks ideal.
Strikes me that you could go lower though... the lower the better really...

 

[Zebra]

Another thing that strikes me though is that you have cement render on your plinth... therefore where is the evaporation going to come from?

 

[dannyg]

Another thing that strikes me though is that you have cement render on your plinth... therefore where is the evaporation going to come from?

Thanks for your reply. Yes I was actually thinking about a retaining wall so keep the ground level below adjacent path. Regarding the plinth, this is actually original and hasn't been touched (I can see the original ashlar lines) and it actually dries out fairly quickly once the rain stops so evaporation seems to be taking plae quite quickly. The wall however was re-rendered in cement by previous owners about 20-30 years ago. They even chopped off the quoins . We plan to remove cement in future and re render whole wall in a more breathable render (lime based). I actually found them in the trench haha. Thankfully the other three walls of the house have their original ashlar facing (we think).